[My apologies. I fumble-fingered WordPress and published a draft version of this article that was incomplete. This is the corrected version. ]

Sometime during the 20th Century, I learned that fuses (or circuit breakers) are used in electrical circuits to prevent catastrophic failure. Fuses open in response to an electrical fault that causes excessive current to flow. The job of the fuse is to minimize the damage and keep things from catching on fire. When I started installing amateur transceivers into vehicles, I learned that you should connect wires directly to the car battery (or darn close) and you should fuse both the positive and negative power leads. I was surprised by the need for two fuses, but there are technical arguments for it. Besides, the transceiver manufacturers recommend it in their manuals. (See figure below.)

I am focusing this discussion on a typical 2m/70cm FM transceiver installation – that is what I have the most experience with and that is the most common ham mobile installation. Such a radio typically draws ~10 A on transmit, so the DC power is usually fused with something like a 15 A (or 20 A) fuse. Keep in mind that a 15 A fuse is not going to protect delicate circuitry but might stop more serious damage or fire.

Connect To The Battery?

Alan/K0BG has an excellent website that provides guidance on mobile radio installations. He points out that modern vehicles usually have an Electrical Load Detector (ELD) inserted into the negative lead of the battery, so that the vehicle control systems can monitor the state of the battery. It is important to connect your radio on the “other side” of the ELD, near where it connects to the vehicle chassis. Oh, and never use the existing vehicle wiring to power your radio (especially not the 12 V accessory plug).

One Fuse or Two Controversy

Recently, I became aware of controversy with regard to proper fusing. Some people are questioning the practice of fusing both DC power leads, while others are vigorously defending it.

For example, there is a lively eham.net discussion here.  Ed/W1RFI provides some useful insight on the ARRL forum.  Alan/K0BG covers the topic of DC power on his wiring and grounding page.  Tom/W8JI argues for the one fuse approach on his website.

What Do The Manufacturers Say?

Generally, you should follow the advice of the manufacturer on any equipment installation, so I took a look at a few owner’s manuals. Most (or all?) of the manuals for the amateur gear show the two fuse method. See the ICOM example below. (Note that they don’t show the presence of the ELD.)

I also took a look at some commercial land mobile radio manuals. Motorola shows the single fuse approach.

Hytera also shows a single fuse in its land mobile manuals.

ICOM makes both amateur and commercial land mobile gear, so I wondered what they recommend for their land mobile product line. Ha, funny thing, they show two fuses, with a comment that says, “Depending on version, the fuse holder may not be attached to the black cable.” Well, isn’t that special?

So is the two-fuse thing some kind of ancient amateur radio practice and the land mobile industry has gone a different path? Sometimes industries adopt “standard” approaches and then forget why with time.

Some Circuit Analysis

After reading through all of the arguments, I tried to distill them down to their essence. I created a wiring diagram that may help explain the concepts. Or maybe not. An automobile is a complex electrical and electronic system, so any practical diagram risks oversimplifying the situation. But here’s my best shot at it.

The center of the diagram shows the body/chassis of the vehicle which is connected to the negative lead of the battery, through the ELD. The transceiver is directly connected to the + terminal of the battery (via Fuse 1) and the chassis side of the ELD (via Fuse 2).  The engine starter is connected to the battery with heavy cables and is also connected to the body/chassis.  While there are a large number of other electrical devices in a modern vehicle, only one is shown here as an example (with a switch and fuse).

The circuit shows the antenna connected to the radio with a coaxial cable. The shield of that cable is almost always grounded to the vehicle chassis at the antenna. (Magnetic mount antennas are one exception and I am sure there are others.) I can say that every mobile installation I’ve ever done had the coaxial cable connected to the chassis. This is an important point because it provides a chassis connection for the transceiver at point C (whether you wanted it or not). There may be other ways that a transceiver is connected to chassis (point B), including the mounting bracket, external speaker, microphone or other accessories.

Arguments For and Against

The argument for fusing the negative lead is to protect against return current from other devices that find its way back to the battery through the transceiver’s negative power lead.  For example, the starter could have a fault in its negative cable, causing the current to flow through the chassis to the transceiver and back to the battery.  The starter current can be hundreds of amperes which would likely overload the radio wire which is sized for 15 amperes. The fuse will open and protect the negative lead (and maybe the radio, to some extent).

The argument against fusing the negative lead is that if the fuse opens up, it could cause problems. Suppose Fuse 2 opens up due to some transient condition. If the transceiver is completely isolated, Fuse 2 would remove power from the transceiver. However, the return path at the antenna coax (point C) will most likely allow the radio to continue functioning using the coax as the negative return. Typically, this is RG-58 or similar cable, which is not intended to carry significant DC current and may fry under the load. If the current is coming from a fault in the starter wiring (big current), this is going to be a bad day for your mobile.

My Conclusions

I think both arguments have merit but choosing one fuse or two requires estimating which problem is most likely and judging the overall impact of the fault. The negative lead fuse can do only one thing well: protect the negative lead. It might provide some protection to the transceiver but there are a lot of sensitive circuits inside the radio that will get destroyed with 15 A flowing. Again, the connection at point C means that the radio will be connected to chassis and current can flow.

If Fuse 2 is eliminated it allows for the flow of high currents through the negative lead of the transceiver. This is not desirable but is it better or worse than the current flowing through the coax shield? Probably better. If a high current device (the starter) has a wiring failure that dumps large currents into the chassis, it may find a number of return paths. Lots of current is going to flow somewhere and potentially cause damage, with or without a negative lead fuse.

I will note that bonding the transceiver to the vehicle chassis has some benefit (point B in the diagram). You may or may not have this connection depending on how you mounted the radio. This electrical connection can shunt any currents away from the coaxial cable, hopefully doing less damage that way.

What am I going to do? My future mobile installations will have only one fuse in the positive lead.  I’ll also bond the radio body to the vehicle chassis, with a hefty, low-resistance connection.

My existing mobile installations all have two fuses. I won’t be changing them out because the risk of inducing a problem with the negative lead fuse is rather low. I don’t see the negative lead fuse as a big risk. If you choose to follow the amateur radio manufacturer’s two fuse recommendation, I understand.

A Request

The amateur radio equipment manufacturers need to give this issue a fresh look. At a minimum, the presence of ELD’s needs to be addressed and the common recommendation of wiring directly to the battery is obsolete. But the one-fuse-or-two issue should also get a careful look by the manufacturer’s engineering teams.

That’s my analysis. What do you think?
(Runs and ducks for cover.)

Note: This article is my technical opinion but my attorney says to tell you that you are responsible if you destroy your vehicle while wiring up your transceiver.

The post Mobile DC Power: One Fuse or Two? appeared first on The KØNR Radio Site.

A few years ago, the Baofeng UV-5R set a new price point for an entry-level handheld transceiver and quickly became the “easy choice” for a newly licensed Technician. It is a very impressive piece of technology for the money (about $30).

However, it is well known that the UV-5R struggles to meet the FCC Part 97 emission requirements. The ARRL lab has published the results of testing a large number of the Baofeng radios and many of them do not meet the FCC spec. Also, the receiver performance is not that great, primarily with respect to adjacent channel and out-of-band rejection. In other words, it is easily overloaded by strong radio signals.

In response, Yaesu created a low-cost radio using similar technology as the UV-5R but with (supposedly) higher quality. This radio escaped my attention when introduced but some recent reviews caught my eye.  In particular, the QST review of the radio includes a detailed lab test report. (The ARRL does a good job with these test reports.)  The review basically says that this radio performs well, especially considering its price class. The price of the radio is currently about $70, so it is more expensive than the UV-5R, but under $100.

Evaluating the FT-4XR

So I went ahead and purchased an FT-4XR to try it out for myself. The main question on my mind is should I recommend the FT-4XR as a good choice for a new radio amateur. I am a license class instructor for our radio club (W0TLM), so I often encounter new hams that are looking for advice on what radio to buy.

My general impression of the FT-4XR is that it looks and feels like a quality product, giving a better first impression than the Baofeng. It fits nicely in my hand and just felt good.

The usability of the FT-4XR is on par with the Baofeng, but a notch down from something like a Yaesu FT-60. In particular, the FT-4XR loads up the keys with multiple functions: press quickly for one function, press and hold for another function, use the “function shift” key for a third function. Yikes! None of this is labeled so you have to memorize all of this or carry a quick reference card with you. Not a huge problem because these are mostly features that are not used frequently or maybe not at all. This means that the FT-4XR is a radio that needs to be set up via programming software to get the desired memories in place. Then, you just choose the right memory / channel.  Not any worse than the Baofeng and similar to many, many radios on the market these days.

The standard FT-4XR manual is adequate but not great. There is an “advanced manual” available on the Yaesu.com web site that may help. The USA version of the radio does not allow transmit outside of the ham bands. This is probably a good thing, especially for a new user. Some people may see this as a disadvantage compared to the Baofeng, which usually transmits over a wider range of frequencies.

Transmitter Harmonics

I trust the ARRL lab tests but I wanted to measure the transmitter to see the harmonic performance up close and personal. The spectrum analyzer measurement below shows the transmitter with very clean harmonics on 2m, just as I would expect from Yaesu. If you look carefully,  you can see a tiny third harmonic just poking up out of the noise floor. (Sorry about the poor graphics, I just took a quick photo of the screen using my phone.)

The 70 cm harmonic performance is also very solid, as shown below.

I also checked the power output, transmit frequency, FM deviation and receiver sensitivity on both bands. Very solid performance. Again, nice job, Yaesu!

Yaesu Inconsistency

One thing I found disappointing is that the radio operation and accessories are not consistent with other Yaesu radios. I’ve got a decent collection of Yaesu handhelds, speaker/microphones, antennas, programming cables, etc. None of these work with the FT-4XR.  In particular, the FT-4XR uses the male SMA connector (same as Baofeng) and requires a new type of programming cable. However, for the first-time buyer, this doesn’t matter and it is no different than buying a Baofeng.

Some other reviews that you may want to consider:

Recommendations

Back to the main question:

Do I recommend the FT-4XR as a good choice for a new radio amateur?

The answer is YES, this is a better radio than the Baofeng UV-5R and it actually meets FCC Part 97 requirements. If you are considering the UV-5R, scrape up a few more bucks and get the FT-4XR.

If you want an even better radio, I’d suggest moving up to something like the tried and true Yaesu FT-60, about $160. It has a more robust receiver and is easier to use.

The post What About the Yaesu FT-4XR? appeared first on The KØNR Radio Site.

Many hams put up some pretty impressive antenna farms with large towers and big arrays. I have a small tower up at the cabin but it is quite puny (about 30 feet) compared to these more serious stations. I like to check out big antenna installations, especially the big commercial towers, as we travel around the country.

There are quite a few radio towers in the range of 2000 feet (~600 meters), as listed on this Wikipedia page.  At 2063 feet, the KVLY-TV mast in North Dakota is the tallest radio mast in the world. The WEAU tower in Wisconsin, listed as 2000 feet, collapsed in 2011 due to a winter ice storm.  Pete/WD4IXD recently pointed me to this video that describes how the tower was rebuilt within one year of the failure. Amazing story!

So you may think your antenna is big but it’s probably not 2000 feet tall.

73 Bob K0NR

The post So You Think You Have a Big Antenna appeared first on The KØNR Radio Site.

For the 2019 CQ Worldwide VHF Contest, I did a modest effort on 6 meters and 2 meters using mostly SSB and FT8. I operated from our cabin (DM78av). We had some good sporadic-E propagation on 6m which enabled some long-distance contacts to the east.  Then I noticed that 2 meters was also open so I quickly turned my attention to that band. While it’s common to have some sporadic E on 6 meters during July, having it on 2 meters is a lot less common. I was thrilled to snag 5 contacts to the eastern US on 2 meters.

One of the 2m contacts was with Jay/W1VD in Connecticut. Shortly after the contest, I got an email from Jay asking about my exact location for the contact, which I supplied using the 6-character grid locator (DM78av).  He told me that it is very difficult to work Colorado on e-skip from Connecticut…the general belief among VHF enthusiasts is that they have to use another propagation mode to work the state. Well, apparently that is not true!

Jay also worked Ken/W0ETT in Parker, CO so this turned into a three-way email discussion. Ken is located about 80 miles to the east of our cabin, so my QSO with W1VD was at a greater distance. Jay investigated the ARRL records and found that these two 2m contacts were notable enough to “make the list” at the ARRL but they are not new distance records. See the ARRL records list here.

Here’s a snippet from the ARRL list, with my W1VD QSO shown as 2793 km (1735 miles). The W0ETT QSO is also shown on the list as 2674 km (1662 miles).

You can see W1VD’s station information on the QSL card above. Obviously, a nice setup. I was using a Yaesu FT-991 driving a Mirage amplifier with 150W output to a 2M9SSB Yagi antenna. My antenna mast is only 25 feet above the ground but I benefit from an excellent radio horizon to the east from 9630 feet in elevation.

73 Bob K0NR

The post A Notable 2m Radio Contact appeared first on The KØNR Radio Site.

Closing out 2019, here are the top five blog posts at k0nr.com during the year. Some people may see this as a lazy way of creating one more blog post for the year without much work. This may be true, but I still claim it is a worthy effort to take a look at what content got the most attention for the year.

Leading the list is this blog post…a perennial favorite that seems to make the top five each year.

Getting Started on 2m SSB

Another popular post that just keeps on going is…

Choose Your 2m Frequency Wisely

A new post this year about VHF propagation comes in third. I am glad to see some new content getting attention.

The Myth of VHF Line-Of-Sight

A bit of a surprise that this post about two proposals for changes to the FCC licensing scheme is in the number four slot:

FCC Considers Changes to Amateur Radio Licensing

Editor’s Choice  

This last one was published in December so it didn’t actually make the top five for the year. However, every time I look at this photo, it gives me a chuckle, so I am including on the list as the Editor’s Choice.

Innovation in Vehicle Labeling

Happy New Year!

73 Bob K0NR

The post Top Five K0NR Blog Posts for 2019 appeared first on The KØNR Radio Site.

Black Forest, Colorado
Sat Feb 22 and 29
8 AM to 5 PM

Black Forest Fire Station
intersection Burgess Rd. & Teachout Rd.

The Technician license is your gateway to the world-wide excitement of Amateur Radio, and the very best emergency communications capability available!

• Earn your ham radio Technician class radio privileges
• Pass your FCC amateur radio license exam right in class on the second day
• Multiple-choice exam, No Morse Code Required
• Live equipment demonstrations
• Learn to operate on the ham bands, 10 Meters and higher
• Learn to use the many VHF/UHF FM repeaters in Colorado
• Find out how to participate in emergency communications

Registration fee: $30 adults, $20 under age 18

In addition, students must have the required study guide: HamRadioSchool.com Technician License Course Third Edition, effective 2018 – 2022, $22.95 print, $19.99 Kindle

Advance registration is required (No later than one week before the first session, earlier is better, first-come sign-up basis until the class is full.)

To register for the class, contact:
Bob Witte KØNR
Email: [email protected] or Phone: 719/659-3727

Sponsored by the Tri-Lakes Monument Radio Association
For more information on amateur (ham) radio visit www.arrl.org

Download:  Tech License Class Flyer – Feb 2020

The post Technician License Class – Black Forest, CO appeared first on The KØNR Radio Site.

Twitter is such a wonderful source of knowledge and a great place to pick up amateur radio operating tips. I saw this post from Johnny/W5KV, talking about getting a 146.52 sticker for his truck. (146.52 MHz is the 2m National Simplex Calling Frequency.) I’ve written about these stickers here: Get Your Mobile Frequency Sticker On

These oval stickers originated in Europe, to indicate the country where a vehicle is registered. In general, these oval stickers have become popular for indicating all kinds of things, including country, state, airport code, national park, etc. One of the most common stickers you’ll see has “26.2” on it to indicate the distance in miles of a marathon run. In other words, it means “I ran a freaking marathon” or maybe “I want you to think I ran a freaking marathon.” You’ll also see “13.1” to indicate the completion of a half marathon.  Hence, W5KV’s comment about 6 full marathons. You will see other numbers used on these stickers, such as “5.56” for you firearms enthusiasts.

So I posted this photo of the back of my truck. My 146.52 is actually a magnetic sign, not a stick-on label but the intent is the same.

But of course, radio amateurs are always innovating to find new ways of doing things. Michael/K2MTS posted this photo of his vehicle with a dust-enabled 146.520 indicator on it.

Like many brilliant innovations, I immediately realized the advantages of using vehicle dust to indicate operating frequency:

• No cost to implement
• Flexibility: the frequency can be easily modified
• Text messages can be appended, such as “CQ CQ” or “Call Me”

One disadvantage is that it requires your vehicle to be dirty but that seems like a minor obstacle, easily overcome by a short drive down a dirt road.

73 Bob K0NR

The post Innovation in Vehicle Labeling appeared first on The KØNR Radio Site.